FactCheck.org has a good analysis of the statements and misstatements made. (Thanks to sleigh for the link.) While both did some spin, Obama nailed McCain several times (eg on Kissinger) and McCain mischaracterized Obama's positions rather desperately (eg Obama didn't vote on a "bill" to raise taxes for people "making as little as $42K"; he voted for a resolution urging the repeal of Bush's tax cuts which would have restored some taxation (some!) down to that level. That was a long time ago and the economic situation has changed... for the worse). McCain was just wrong about the letter Ike wrote before D-Day and how earmarks have "tripled" in the last few years (they've declined, especially since the Democrats took both houses of Congress).
It seemed McCain was winging it in the beginning, and came off a poor second. Later, he started slinging Republican talking points (calling Obama "the most liberal senator" which may play to the goppie "base" but is a high compliment for many) and getting back to his stump speech. Obama had gravitas and McCain had barely restrained passion. McCain is losing, and the Palin pick is turning into a disaster. He needed to do much better than Obama, and he came off as barely holding his own against a superior leader.
For over a year, the 24-hour "news" channels have been pretending the overnight polls actually mattered. Well, now they do, and they all favor Obama.
Aside: I don't like to pillory people for being mostly right but wrong in specifics, especially when I agree with them. McCain said he would "fire" SEC head Cox when the president doesn't have the power to do that. In the debate, he ameliorated that to "call for his resignation" which is fairly similar (a president can put a lot of pressure on people he doesn't have direct control over) and I tend to agree that Cox (among others) should go.
Similarly, Obama kept saying Iraq has a $79 billion surplus. It was projected that high, but is likely to come in at about $60 billion. That's still far more than the $10 billion we're sending to the country